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Inhalation toxicity of nanoparticle-based aerosols

: Gessner, Isabel
: Mathur, Sanjay; Knebel, Jan W.; Dasenbrock, Clemens

Köln, 2014, VII, 73 S.
Köln, Univ., Master Thesis, 2014
Master Thesis
Fraunhofer ITEM ()
inhalation toxicology; nanoparticles - toxicology; aerosols; nanoparticles - health aspects

Although human exposure to nanoparticles (NPs) continuously rises due to a rapid increase in their production and application, the adverse effects towards humans are often only rarely studied. Air/liquid interface (ALI) exposure methods are the preferred in-vitro systems for testing airborne substances with regard to inhalation toxicology. Cells are thereby grown on microporous membranes, fed by culture medium on the basal side and air lifted on the apical side. In this work, a nano-sized positive control was searched in order to evaluate the air/liquid technique by use of a newly invented type of exposure system (P.R.I.T.® ExpoCube®). For this reason, three different spinel ferrite nanoparticles (MFe2O4 with M = Cu, Co, Ni) were prepared via a solvothermal process and characterised by X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Crystalline metal oxide particles were produced with diameters ranging from 2 to 5 nm.
Submerged in-vitro toxicity screening assays revealed a low toxic potential in human lung epithelial (A549) cells for all three types of polyvinylpyrrolidone (PVP) coated spinel ferrites with EC50 values ranging from 0.75 mg/ml in terms of CuFe2O4 to 2.1 mg/ml and 4.01 mg/ml in terms of NiFe2O4 and CoFe2O4, respectively. Cell viability was determined using water soluble tetrazolium salt assay (WST-1). For comparison, two other metal oxide nanoparticles with known cytotoxic potential (ZnO, CuO) were likewise assessed resulting in distinctly lower EC50 values (ZnO = 48 g/ml, CuO = 23 g/ml). Out of all particles tested, copper oxide nanoparticles were clearly the most potent toxic materials. Based on these results, CuO particles were examined more closely with respect to their suitability as positive control.
After aerosolisation of CuO NPs and acute exposures to A549 cells in ALI experiments, no adverse effects were observed. Similar results were obtained, when the particles were dispersed in surfactant and tested at the air/liquid interface, compared to submerged exposure studies. The fact that distinctly higher doses were necessary in ALI experiments could be explained by the release of Cu2+-ions which got diluted by the basal medium in ALI experiments. Indeed, it could be demonstrated that the high toxic potential of copper oxide nanoparticles is dependent on both, the soluble and the insoluble characteristics. Although CuO-NPs might not be suitable as general positive control for ALI experiments, they might be of interest as reference substance for other partly soluble particles. The applicability of the P.R.I.T.® exposure setup for in-vitro evaluation of nanoparticle-based aerosols was proven by further increasing the particle concentration at the air/liquid interface using chronic exposures over two to three days. Significant toxic effects were measurable, even at low deposited particles masses.